1. Field of the Invention
The present invention relates to a technique that controls idling stop of an internal combustion engine, which is carried out according to the driving state of a vehicle.
2. Description of the Related Art
Some proposed vehicles have an idling stop control function that stops driving an internal combustion engine at a temporary stop of the vehicle, for example, at a traffic light during a drive of the vehicle, and restarts driving the internal combustion engine in response to a driver""s requirement for a start. In such vehicles having the function of automatically stopping and restarting the operation of the internal combustion engine, an auxiliary machinery driving electric electric motor is linked with the internal combustion engine and auxiliary machinery via fan belts to allow mutual connection thereof. While the internal combustion engine is at a stop, the auxiliary machinery like a water pump is driven by means of the auxiliary machinery driving electric electric motor. In the active state of the internal combustion engine, on the other hand, the auxiliary machinery is driven by means of the internal combustion engine. In order to disconnect the internal combustion engine from the driving system and reduce the loading of the auxiliary machinery driving electric electric motor while the auxiliary machinery is driven by means of the auxiliary machinery driving electric electric motor, a clutch (coupling mechanism) is interposed between the internal combustion engine and the auxiliary machinery driving electric electric motor to couple and release the internal combustion engine with and from the auxiliary machinery driving electric motor.
The auxiliary machinery driving electric motor also functions as the electric motor that restarts driving the internal combustion engine. At a start of driving the internal combustion engine, the clutch couples the internal combustion engine with the auxiliary machinery driving electric motor, which is currently driving the auxiliary machinery. This raises the velocity of the internal combustion engine to a starting speed of revolutions. One proposed technique couples the clutch after reduction of the velocity of the auxiliary machinery driving electric motor at a restart of driving the internal combustion engine, in order to reduce the occurrence of potential shocks and vibrations due to the velocity difference between the internal combustion engine and the auxiliary machinery driving electric motor, which is currently driving the auxiliary machinery.
In some driving states of the vehicle, the shocks and vibrations (energy) arising due to the coupling action of the clutch are not sufficiently absorbed by the fan belt. For example, in the cold time, partly because of the low temperature of the fan belt, the shocks and vibrations occurring due to the coupling action of the clutch are not sufficiently absorbed in the course of restarting the internal combustion engine under the idling stop control. Enhancing the rate of decrease in number of revolutions of the auxiliary machinery driving electric motor or in electric motor velocity to ensure the sufficient absorption, on the other hand, does not fulfil the requirement of quick restart of the internal combustion engine.
The object of the present invention is thus to reduce or even omit potential shocks and vibrations arising due to the coupling action of a coupling mechanism at the. time of starting an internal combustion engine, and to ensure a quick restart of the internal combustion engine.
At least part of the above and the other related objects is attained by an idling stop control apparatus mounted on a vehicle, wherein auxiliary machinery is driven by means of either one of an internal combustion engine and an electric motor, and an output shaft of the internal combustion engine and an output shaft of the electric motor are linked with each other via a coupling mechanism that is coupled to connect the internal combustion engine with the electric motor and is released to disconnect the internal combustion engine from the electric motor. The coupling mechanism is released and the auxiliary machinery is driven by means of the electric motor via a transmission belt while the internal combustion engine is at a stop. The idling stop control apparatus includes: a decision unit that determines whether a driving stop condition or a driving restart condition of the internal combustion engine is fulfilled; a braking load specification unit that, when the driving restart condition of the internal combustion engine is fulfilled, specifies a braking load to be applied to the electric motor, in order to reduce electric motor velocity or number of revolutions of the electric motor according to a kinetic energy absorbing state of the transmission belt; a drive stand-by unit that, when the driving restart condition of the internal combustion engine is fulfilled and the coupling mechanism is released, causes the output shaft of the internal combustion engine to be coupled with the output shaft of the electric motor via the coupling mechanism after application of the specified braking load to the electric motor; and an internal combustion engine operation control unit that executes a series of processing to restart operation of the internal combustion engine after the internal combustion engine is coupled with the electric motor via the coupling mechanism.
In the idling stop control apparatus of the present invention, the braking load to be applied to the electric motor is specified, in order to reduce the number of revolutions of the electric motor or the electric motor velocity according to the kinetic energy absorbing state of the transmission belt. This arrangement effectively reduces or even omits potential shocks and vibrations arising due to the coupling action of the coupling mechanism at the time of starting the internal combustion engine, and ensures a quick restart of the internal combustion engine.
In accordance with one aspect of the idling stop control apparatus of the present invention, the vehicle has a transmission belt elasticity measurement unit that measures elasticity of the transmission belt, and the braking load specification unit determines the kinetic energy absorbing state of the transmission belt based on the observed elasticity of the transmission belt and increases the braking load with a decrease in observed elasticity of the transmission belt. In accordance with another aspect, the vehicle has a transmission belt temperature measurement unit that measures temperature of the transmission belt, and the braking load specification unit determines the kinetic energy absorbing state of the transmission belt based on the observed temperature of the transmission belt and increases the braking load with a decrease in observed temperature of the transmission belt.
The kinetic energy absorbing state of the transmission belt represents the state that is capable or incapable of sufficiently absorbing energy like shocks and vibrations, and correlates with the properties, such as the elasticity and the hardness, of the transmission belt. Namely measurement of the elasticity of the transmission belt results in specifying the kinetic energy absorbing state of the transmission belt. The properties like the elasticity and the hardness of the transmission belt correlate with the temperature of the transmission belt. These properties can thus be specified according to the temperature of the transmission belt. Under the condition of low temperatures, the transmission belt tends to be cured and lose its elasticity and thus hardly absorbs the potential shocks and vibrations (energy) arising due to the coupling action of the coupling mechanism. Under the condition of high temperatures, on the contrary, the transmission belt readily absorbs the potential shocks and vibrations arising due to the coupling action of the coupling mechanism. The arrangement of varying the braking load by taking into account such conditions attains both the requirement of absorbing potential shocks and vibrations arising due to the coupling action of the coupling mechanism and the requirement of quickly restarting the internal combustion engine.
In one example of the above aspect that measures the temperature of the transmission belt, the transmission belt temperature measurement unit is a cooling fluid temperature measurement unit that measures temperature of a cooling fluid passing through the internal combustion engine. The braking load specification unit determines the kinetic energy absorbing state of the transmission belt based on the observed temperature of the cooling fluid and increases the braking load with a decrease in observed temperature of the cooling fluid. This arrangement enables the temperature of the transmission belt to be obtained indirectly.
In another aspect of this application, the transmission belt temperature measurement unit is an engine velocity accumulation unit that accumulates engine velocity or number of revolutions of the internal combustion engine from a start to a stop of driving of the internal combustion engine. In this aspect, the braking load specification unit determines the kinetic energy absorbing state of the transmission belt based on the accumulated engine velocity and decreases the braking load with an increase in accumulated engine velocity. In still another aspect of this application, the transmission belt temperature measurement unit is an electric motor velocity accumulation unit that accumulates electric motor velocity or number of revolutions of the electric motor after a stop of driving of the internal combustion engine. In this aspect, the braking load specification unit determines the kinetic energy absorbing state of the transmission belt based on the accumulated electric motor velocity and decreases the braking load with an increase in accumulated electric motor velocity. These arrangements enable the temperature of the transmission belt to be obtained by taking into account the frictional heat evolved due to the sliding motions.
In either one of the above aspects, the transmission belt temperature measurement unit further includes an outside air temperature measurement unit that measures outside air temperature, and the braking load specification unit increases a rate of decrease of the braking load with an increase in observed outside air temperature. This arrangement enables the temperature of the transmission belt to be obtained by taking into account the outside air temperature.
The present invention is also directed to a first vehicle having an idling stop function to selectively stop and restart driving an internal combustion engine according to a driving state of the vehicle, wherein auxiliary machinery is driven by means of an electric motor while the internal combustion engine is at a stop and by means of the internal combustion engine while the internal combustion engine is in active state. The first vehicle includes: a coupling mechanism that links an output shaft of the internal combustion engine with an output shaft of the electric motor, such as to be coupled to connect the internal combustion engine with the electric motor and to be released to disconnect the internal combustion engine from the electric motor; a transmission belt that is laid through the output shaft of the internal combustion engine, an input shaft of the auxiliary machinery, and the output shaft of the electric motor; a transmission belt state detection unit that detects a kinetic energy absorbing state of the transmission belt; and an idling stop control unit that specifies a rate of decrease in electric motor velocity or number of revolutions of the electric motor based on the detected kinetic energy absorbing state of the transmission belt, and when a driving restart condition for restarting operation of the internal combustion engine is fulfilled, lowers the electric motor velocity by the specified rate of decrease, causes the output shaft of the internal combustion engine to be coupled with the output shaft of the electric motor via the coupling mechanism, and subsequently carries out a series of processing to restart driving the internal combustion engine.
In the first vehicle of the present invention, the rate of decrease in electric motor velocity is specified based on the kinetic energy absorbing state of the transmission belt. This arrangement effectively reduces or even omits potential shocks and vibrations arising due to the coupling action of the coupling mechanism at the time of starting the internal combustion engine, and enables the vehicle to be quickly restored to the drivable state.
In accordance with one preferable application of the first vehicle of the present invention, the transmission belt state detection unit detects the kinetic energy absorbing state of the transmission belt based on elasticity of the transmission belt, and the idling stop control unit enhances the rate of decrease in electric motor velocity with a decrease in elasticity of the transmission belt. In accordance with another preferable application of the first vehicle of the present invention, the transmission belt state detection unit detects the kinetic energy absorbing state of the transmission belt based on temperature of the transmission belt, and the idling stop control unit enhances the rate of decrease in electric motor velocity with a decrease in temperature of the transmission belt.
In one aspect of the above application that takes into account the temperature of the transmission belt, the vehicle further includes: a heat dissipation unit that is arranged on a windward side of the transmission belt to dissipate heat of a cooling fluid, which has passed through and cooled down the internal combustion engine; and a cooling fluid temperature measurement unit that measures temperature of the cooling fluid. In this aspect, the transmission belt state detection unit calculates the temperature of the transmission belt from the observed temperature of the cooling fluid and detects the kinetic energy absorbing state of the transmission belt based on the calculated temperature of the transmission belt. In this structure, the transmission belt is affected by the amount of heat dissipated by the heat dissipation unit, that is, by the temperature of the cooling fluid. Measurement of the temperature of the cooling fluid thus enables the temperature of the transmission belt to be obtained indirectly.
In another aspect of this application, the vehicle further includes an engine velocity accumulation unit that accumulates engine velocity or number of revolutions of the internal combustion engine from a start to a stop of driving of the internal combustion engine. In this aspect, the transmission belt state detection unit calculates the temperature of the transmission belt from the accumulated engine velocity and detects the kinetic energy absorbing state of the transmission belt based on the calculated temperature of the transmission belt. In still another aspect of this application, the vehicle further includes an electric motor velocity accumulation unit that accumulates electric motor velocity or number of revolutions of the electric motor after a stop of driving of the internal combustion engine. In this aspect, the transmission belt state detection unit calculates the temperature of the transmission belt from the accumulated electric motor velocity and detects the kinetic energy absorbing state of the transmission belt based on the calculated temperature of the transmission belt. These arrangements enable the temperature of the transmission belt to be obtained by taking into account the frictional heat evolved due to the sliding motions.
In either one of the above aspects, the vehicle further includes an outside air temperature measurement unit that measures outside air temperature. The transmission belt state detection unit calculates the temperature of the transmission belt from the observed outside air temperature in addition to at least one of the observed temperature of the cooling fluid, the accumulated engine velocity, and the accumulated electric motor velocity and detects the kinetic energy absorbing state of the transmission belt based on the calculated temperature of the transmission belt. This arrangement enables the temperature of the transmission belt to be obtained by taking into account the outside air temperature.
In the first vehicle having any of the above configurations, the idling stop control unit stops driving the internal combustion engine and releases the coupling mechanism when a driving stop condition of the internal combustion engine is fulfilled.
The present invention is further directed to a second vehicle having an idling stop function to selectively stop and restart driving an internal combustion engine according to a driving state of the vehicle, wherein auxiliary machinery is driven by means of an electric motor via a transmission belt while the internal combustion engine is at a stop and by means of the internal combustion engine while the internal combustion engine is in active state. The second vehicle includes: a coupling mechanism that links an output shaft of the internal combustion engine with an output shaft of the electric motor, such as to be coupled to connect the internal combustion engine with the electric motor and to be released to disconnect the internal combustion engine from the electric motor; a target braking velocity determination unit that determines a target braking velocity for braking the electric motor prior to a restart of driving of the internal combustion engine by taking into account temperature of the transmission belt; and an idling stop control unit that, when a driving restart condition for restarting operation of the internal combustion engine is fulfilled, drives the electric motor at the target braking velocity, causes the output shaft of the internal combustion engine to be coupled with the output shaft of the electric motor via the coupling mechanism, and subsequently carries out a series of processing to restart driving the internal combustion engine.
In the second vehicle of the present invention, the target braking velocity for braking the electric motor is determined by taking into account the temperature of the transmission belt. This arrangement effectively reduces or even omits potential shocks and vibrations arising due to the coupling action of the coupling mechanism at the time of starting the internal combustion engine, and enables the vehicle to be quickly restored to the drivable state.
In accordance with one preferable application of the present invention, the second vehicle further includes: a heat dissipation unit that is arranged on a windward side of the transmission belt to dissipate heat of a cooling fluid, which has passed through and cooled down the internal combustion engine; and a cooling fluid temperature measurement unit that measures temperature of the cooling fluid. In this application, the target braking velocity determination unit takes into account the temperature of the transmission belt based on the observed temperature of the cooling fluid and lowers the target braking velocity with a decrease in observed temperature of the cooling fluid. In this structure, the transmission belt is affected by the amount of heat dissipated by the heat dissipation unit, that is, by the temperature of the cooling fluid. Measurement of the temperature of the cooling fluid thus enables the temperature of the transmission belt to be taken into account.
Like the first vehicle discussed above, in the second vehicle of the present invention, the target braking velocity determination unit takes into account the temperature of the transmission belt based on the accumulated engine velocity or the accumulated electric motor velocity, namely based on the frictional heat evolved due to the sliding motions. The rate of increase in target braking velocity may be varied according to the observed outside air temperature.
In the second vehicle having any of the above configurations, the idling stop control unit stops driving the internal combustion engine and releases the coupling mechanism when a driving stop condition of the internal combustion engine is fulfilled.
The present invention is also directed to a method of controlling idling stop in a vehicle that has an idling stop function to selectively stop and restart driving an internal combustion engine according to a driving state of the vehicle, wherein auxiliary machinery is driven by means of an electric motor while the internal combustion engine is at a stop. The method includes the steps of: detecting a kinetic energy absorbing state of a transmission belt that is laid through the internal combustion engine, the electric motor, and the auxiliary machinery; determining whether or not a driving restart condition for restarting operation of the internal combustion engine is fulfilled; when it is determined that the driving restart condition is fulfilled, specifying a rate of decrease in electric motor velocity or number of revolutions of the electric motor based on the detected kinetic energy absorbing state of the transmission belt; and lowering the electric motor velocity by the specified rate of decrease and subsequently causing the output shaft of the internal combustion engine to be coupled with the output shaft of the electric motor via the coupling mechanism, so as to restart driving the internal combustion engine.
In the method of the present invention, the rate of decrease in electric motor velocity is specified based on the kinetic energy absorbing state of the transmission belt. This arrangement effectively reduces or even omits potential shocks and vibrations arising due to the coupling action of the coupling mechanism at the time of starting the internal combustion engine, and ensures a quick restart of the internal combustion engine.
In accordance with one preferable application of the present invention, the method further includes the steps of: measuring elasticity of the transmission belt; detecting the kinetic energy absorbing state of the transmission belt based on the observed elasticity of the transmission belt; and enhancing the rate of decrease in electric motor velocity with a decrease in observed elasticity of the transmission belt. In accordance with another preferable application of the present invention, the method further includes the steps of: measuring temperature of the transmission belt; detecting the kinetic energy absorbing state of the transmission belt based on the observed temperature of the transmission belt; and enhancing the rate of decrease in electric motor velocity with a decrease in observed temperature of the transmission belt. The kinetic energy absorbing state of the transmission belt in the method is synonymous with the kinetic energy absorbing state of the transmission belt in the idling stop control apparatus of the present invention discussed above.
In one aspect of the above application that measures the temperature of the transmission belt, the method further includes the steps of: measuring temperature of a cooling fluid that passed through the internal combustion engine; and enhancing the rate of decrease in electric motor velocity with a decrease in observed temperature of the cooling fluid. This arrangement enables the temperature of the transmission belt to be obtained indirectly.
In another aspect of this application, the method further includes the steps of: accumulating engine velocity or number of revolutions of the internal combustion engine from a start to a stop of driving of the internal combustion engine; and lowering the rate of decrease in electric motor velocity with an increase in accumulated engine velocity. In still another aspect of this application, the method further includes the steps of: accumulating electric motor velocity or number of revolutions of the electric motor after a stop of driving of the internal combustion engine; and lowering the rate of decrease in electric motor velocity with an increase in accumulated electric motor velocity. These arrangements enable the temperature of the transmission belt to be obtained by taking into account the frictional heat evolved due to the sliding motions.
In either one of the above aspects, the method further includes the steps of: measuring an outside air temperature; and enhancing the rate of decrease in electric motor velocity with an increase in observed outside air temperature. This arrangement enables the rate of decrease in electric motor velocity to be varied according to the observed outside air temperature.
These and other objects, features, aspects, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiment with the accompanying drawings.